UPSC Prelims 2021 CSAT Paper II · Q4 of 79 Comprehension medium

Passage

Passage - 4 Researchers were able to use stem cells to gauge the neurotoxic effects of the environmental pollutant Bisphenol A (BPA). They used a combination of biochemical and cell-based assays to examine the gene expression profile during the differentiation of mouse embryonic stem cells upon treatment with BPA, a compound known to cause heart diseases, diabetes, and developmental abnormalities in humans. They were able to detect and measure BPA toxicity towards the proper specification of primary germ layers, such as endoderm and ectoderm, and the establishment of neural progenitor cells.

On the basis of the passage given above, the following assumptions have been made : 1. BPA may alter embryonic development in vivo. 2. Biochemical and cell-based assays are useful in finding out treatments for pollution-induced diseases. 3. Embryonic stem cells could serve as a model to evaluate the physiological effects of environmental pollutants. Which of the above assumptions are valid ?

  1. (a) 1 and 2 only
  2. (b) 2 and 3 only
  3. (c) 1 and 3 only ✓ UPSC's answer
  4. (d) 1, 2 and 3

Why the answer is (c)

• Assumption 1 is valid because the passage states BPA causes developmental abnormalities in humans and affects germ layer specification in stem cells, implying it can alter embryonic development in vivo.

• Assumption 3 is valid because the researchers successfully used mouse embryonic stem cells to gauge neurotoxic effects, proving they serve as a model for evaluating physiological effects of pollutants.

• Assumption 2 is invalid because the passage describes using assays to examine gene expression and detect toxicity, not to find treatments for pollution-induced diseases.

• Since assumptions 1 and 3 are supported by the text while assumption 2 is not, the correct combination is 1 and 3 only.

Why the other options are wrong

(a) 1 and 2 only
Assumption 2 is invalid as the passage does not mention finding treatments for pollution-induced diseases.
(b) 2 and 3 only
Assumption 2 is invalid as the passage does not mention finding treatments for pollution-induced diseases.
(d) 1, 2 and 3
Assumption 2 is invalid as the passage does not mention finding treatments for pollution-induced diseases.

Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2021, held on 10 October 2021. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.

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